1. Field of the Invention
The present invention relates to a wire bonding apparatus and also to a wire bonding method.
2. Description of the Related Art
FIG. 11 illustrates a conventional method of wire bonding in which a connecting electrode 22 on a circuit board 21 is wire-bonded by means of a wire 25 to an external lead terminal 24 which is provided on a package 23 and which is vertically and horizontally staggered from the electrode 22. If the wire bonding is done such as to minimize the length of the wire 25, the wire 25 may be abnormally stressed in the event that the relative positions of the electrode 22 and the terminal 24 to each other are changed due to a change in the ambient temperature, thus impairing the reliability of the whole device. In order to obviate this problem, hitherto, the wire 25 is slacked both in the vertical and horizontal directions so as to absorb any tension, as illustrated in FIGS. 12 and 13.
Vertical slacking of the wire 23 by a height H as illustrated in FIG. 12 requires an additional space for accommodating the slack height H, while horizontal slacking of the wire 25 by a length L.sub.1 as illustrated in FIG. 13 requires an additional space for accommodating the slack length L.sub.1, thus impairing the space factor. In the case of FIG. 13, the overall size of the package is undesirably increased due to increased distance L.sub.2 between the connecting electrode 22 and the external lead terminal 24.